German Offenlegungsschrift No. 16 53 181 teaches a device for wetting wood fibers with liquid binder, which device has a mixing drum rotatable about its center lengthwise axis. In a fixed position with respect to the mixing drum the device consists of one spiked roller with a cover plate or two spiked rollers rotating in opposite directions located in the vicinity of the ascending mixing drum wall, by means of which device wood fibers rising with the mixing drum wall are thrown back at the same speed and in the same direction to the wood fiber bed located in the lower region of the mixing drum. Spray nozzles which spray liquid binder onto the wood fibers as they move by are located immediately above this trajectory. With this device, insufficiently uniform distribution of the binder on the wood fibers is unavoidable. The same is true when such a device is used for coating wood chips with glue. The reason for this is that the binder sprayed directly onto the wood fibers cannot be subjected to a distribution process on the surfaces of the fibers.
It is already known that powdered binder can be blown onto the wood chips together with compressed air by means of devices with the same basic design. Here, too, nonuniform distribution of the binder is unavoidable. Furthermore, removal of the air introduced additionally into the interior space of the mixing drum poses considerable problems.